Answers for "how to throw error in java"

throw io exception java

public static void foo() throws IOException {
    // some code here, when something goes wrong, you might do:
    throw new IOException("error message");
}

public static void main(String[] args) {
    try {
        foo();
    } catch (IOException e) {
        System.out.println(e.getMessage());
    }
}

in java how to throw exception from function

public void doChangePin(int oldPin, int pin) throws Exception {	//need to add throws followed by exception name
		if (oldPin == pinCode) {
			pinCode = pin;
		} else {
			throw new Exception("some message");	//throwing the exception by creating its new object
		}
	}

java throw an exception

public static void main(String[] args) {
	Scanner kb = new Scanner(System.in);
    System.out.println("Enter a number");
    try {
    	double nb1 = kb.nextDouble();
    	if(nb1<0)
        	throw new ArithmeticException();
        else System.out.println( "result : " + Math.sqrt(nb1) );
    } catch (ArithmeticException e) {
        System.out.println("You tried an impossible sqrt");
    }
}

throw keyword in java

Generally JVM throws the exception and
we handle the exceptions by 
using try catch block. But there are
situations where we have to throw 
userdefined exceptions or runtime exceptions.
  In such case we use throw keyword 
to throw exception explicitly.

  Syntax : throw throwableInstance;